Nature and extent of the burden and risks associated with participation, benefit and group relatedness: From a patient's perspective, the burden of daily immunoadsorption is comparable with that of daily plasma exchange with regard to vascular access (central venous catheter) and blood sampling to monitor treatment response. The treatment time is approximately one hour longer than plasma exchange (4 hours instead of 3 hours). Possible adverse effects of immunoadsorption are part of the current study proposal but previous studies in other patient groups suggest that frequency and severity of adverse effects of immunoadsorption are comparable with plasma exchange.